U.S. patent application number 16/804902 was filed with the patent office on 2020-09-03 for light modulation apparatus, optical module, and projector.
This patent application is currently assigned to SEIKO EPSON CORPORATION. The applicant listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Tomoharu MASUDA, Kohei NAKAZAKI, Masanori YASUDA.
Application Number | 20200278597 16/804902 |
Document ID | / |
Family ID | 1000004689542 |
Filed Date | 2020-09-03 |
United States Patent
Application |
20200278597 |
Kind Code |
A1 |
MASUDA; Tomoharu ; et
al. |
September 3, 2020 |
LIGHT MODULATION APPARATUS, OPTICAL MODULE, AND PROJECTOR
Abstract
A light modulation includes a light modulator, a first polarizer
wherein light outputted from the light modulator is incident, and a
second polarizer wherein light outputted from the first polarizer
is incident. The first polarizer includes a first base having a
first and second surface, a first light absorbing layer to face the
first base, and a first inorganic polarization layer on the first
surface, disposed between the first base and first light layer. The
second polarizer includes a second base having a third and fourth
surface, a second light absorbing layer to face the second base,
and a second inorganic polarization layer on the third surface,
disposed between the second base and second light layer. The first
polarizer is disposed the first light layer faces a light exiting
surface. The second polarizer is disposed the fourth surface of the
second base faces the second surface of the first base.
Inventors: |
MASUDA; Tomoharu;
(Matsumoto-shi, JP) ; YASUDA; Masanori;
(Matsumoto-shi, JP) ; NAKAZAKI; Kohei;
(Matsumoto-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
1000004689542 |
Appl. No.: |
16/804902 |
Filed: |
February 28, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 27/1046 20130101;
G03B 21/147 20130101; G02F 1/133528 20130101; G02F 2001/133548
20130101; G03B 21/006 20130101; G02F 1/133512 20130101 |
International
Class: |
G03B 21/14 20060101
G03B021/14; G02F 1/1335 20060101 G02F001/1335; G02B 27/10 20060101
G02B027/10; G03B 21/00 20060101 G03B021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2019 |
JP |
2019-035562 |
Feb 28, 2019 |
JP |
2019-035570 |
Claims
1. A light modulation apparatus comprising: a light modulator that
modulates light; a first polarizer on which light outputted from
the light modulator is incident; and a second polarizer on which
light outputted from the first polarizer is incident, wherein the
first polarizer includes a first base having a first surface and a
second surface, a first light absorbing layer so provided as to
face the first base, and a first inorganic polarization layer
provided on the first surface and disposed between the first base
and the first light absorbing layer, the second polarizer includes
a second base having a third surface and a fourth surface, a second
light absorbing layer so provided as to face the second base, and a
second inorganic polarization layer provided on the third surface
and disposed between the second base and the second light absorbing
layer, the first polarizer is so disposed that the first light
absorbing layer faces a light exiting surface of the light
modulator, and the second polarizer is so disposed that the fourth
surface of the second base faces the second surface of the first
base.
2. The light modulation apparatus according to claim 1, wherein the
first inorganic polarization layer is a wire-grid polarization
layer.
3. The light modulation apparatus according to claim 1, wherein the
second inorganic polarization layer is a wire-grid polarization
layer.
4. The light modulation apparatus according to claim 1, wherein at
least one of the first and second bases is made of low thermal
expansion glass.
5. An optical module comprising: a first light modulation apparatus
that modulates first color light; a second light modulation
apparatus that modulates second color light; a third light
modulation apparatus that modulates third color light; and a light
combiner that combines the first color light modulated by the first
light modulation apparatus, the second color light modulated by the
second light modulation apparatus, and the third color light
modulated by the third light modulation apparatus to produce
combined light, wherein at least one of the first light modulation
apparatus, the second light modulation apparatus, and the third
light modulation apparatus is the light modulation apparatus
according to claim 1.
6. A projector comprising: a light source apparatus that outputs
light; the optical module according to claim 5 on which the light
outputted from the light source apparatus is incident and which
outputs the combined light; and a projection optical apparatus that
projects the combined light outputted from the optical module on a
projection surface.
7. A projector comprising: a light source apparatus that outputs
light; the light modulation apparatus according to claim 1 that
modulates the light outputted from the light source apparatus; and
a projection optical apparatus that projects the light modulated by
the light modulation apparatus on a projection surface.
8. A projector comprising: a light source apparatus that outputs
light; the light modulation apparatus according to claim 2 that
modulates the light outputted from the light source apparatus; and
a projection optical apparatus that projects the light modulated by
the light modulation apparatus on a projection surface.
9. A projector comprising: a light source apparatus that outputs
light; the light modulation apparatus according to claim 3 that
modulates the light outputted from the light source apparatus; and
a projection optical apparatus that projects the light modulated by
the light modulation apparatus on a projection surface.
10. A projector comprising: a light source apparatus that outputs
light; the light modulation apparatus according to claim 4 that
modulates the light outputted from the light source apparatus; and
a projection optical apparatus that projects the light modulated by
the light modulation apparatus on a projection surface.
Description
[0001] The present application is based on, and claims priority
from JP Application Serial Numbers 2019-035562 and 2019-035570,
both filed Feb. 28, 2019, the disclosure of which is hereby
incorporated by reference herein in its entirety.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a light modulation
apparatus, an optical module, and a projector.
2. Related Art
[0003] In a light modulation apparatus that forms a projector, to
increase the extinction ratio of a light-exiting-side polarizing
plate of a liquid crystal panel for an increase in contrast of a
projection image, there has been a proposal to employ a
configuration in which the light-exiting-side polarizing plate is
formed of two polarizing plates.
[0004] For example, JP-A-2009-3106 discloses a projector having a
configuration in which an inorganic polarizing plate and an organic
polarizing plate are disposed on the light exiting side of the
liquid crystal panel in the presented order from the side facing
the liquid crystal panel. JP-A-2009-3106 describes that the use of
the inorganic polarizing plate and the organic polarizing plate
provides a high extinction ratio and high optical transparency as
the entire polarizing plate because a typical organic polarizing
plate provides a high extinction ratio and high optical
transparency.
[0005] Employing an organic polarizing plate as part of the
light-exiting-side polarizing plate, as in the projector described
in JP-A-2009-3106, however, has a problem of a decrease in
reliability of the projector because an organic polarizing plate is
greatly degraded due to light as compared with an inorganic
polarizing plate. In contrast, employing an inorganic polarizing
plate is likely to produce stray light and return light in the
space between the inorganic polarizing plate and a downstream light
combining prism or projection system because the inorganic
polarizing plate includes a high-reflectance inorganic polarization
layer whereas improving the reliability, resulting in a problem of
a ghost and light leakage due to the stray light and the return
light.
SUMMARY
[0006] A light modulation apparatus according to an aspect of the
present disclosure includes a light modulator that modulates light,
a first polarizer on which light outputted from the light modulator
is incident, and a second polarizer on which light outputted from
the first polarizer is incident. The first polarizer includes a
first base having a first surface and a second surface, a first
inorganic polarization layer provided on the first surface, and a
first light absorbing layer so provided as to face the first base
with the first inorganic polarization layer sandwiched between the
first base and the first light absorbing layer. The second
polarizer includes a second base having a third surface and a
fourth surface, a second inorganic polarization layer provided on
the third surface, and a second light absorbing layer so provided
as to face the second base with the second inorganic polarization
layer sandwiched between the second base and the second light
absorbing layer. The first polarizer is so disposed that the first
light absorbing layer faces a light exiting surface of the light
modulator. The second polarizer is so disposed that the fourth
surface of the second base faces the second surface of the first
base.
[0007] In the light modulation apparatus according to the aspect of
the present disclosure, the first inorganic polarization layer may
be formed of a wire-grid polarization layer.
[0008] In the light modulation apparatus according to the aspect of
the present disclosure, the second inorganic polarization layer may
be formed of a wire-grid polarization layer.
[0009] In the light modulation apparatus according to the aspect of
the present disclosure, at least one of the first and second bases
may be made of low thermal expansion glass.
[0010] An optical module according to another aspect of the present
disclosure includes a first light modulation apparatus that
modulates first color light based on an image signal, a second
light modulation apparatus that modulates second color light based
on an image signal, a third light modulation apparatus that
modulates third color light based on an image signal, and a light
combiner that combines the first color light modulated by the first
light modulation apparatus, the second color light modulated by the
second light modulation apparatus, and the third color light
modulated by the third light modulation apparatus with one another
to produce combined light, and at least one of the first light
modulation apparatus, the second light modulation apparatus, and
the third light modulation apparatus is the light modulation
apparatus according to the aspect of the present disclosure.
[0011] A projector according to another aspect of the present
disclosure includes a light source apparatus that outputs light,
the optical module according to the other aspect of the present
disclosure on which the light outputted from the light source
apparatus is incident and which outputs the combined light, and a
projection optical apparatus that projects the combined light
outputted from the optical module on a projection receiving
surface.
[0012] A projector according to still another aspect of the present
disclosure includes a light source apparatus that outputs light, a
light modulation apparatus that modulates the light outputted from
the light source apparatus based on an image signal, and a
projection optical apparatus that projects the light modulated by
the light modulation apparatus on a projection receiving surface,
and the light modulation apparatus is the light modulation
apparatus according to the aspect of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic configuration diagram of a projector
according to a first embodiment.
[0014] FIG. 2 is a schematic configuration diagram of an optical
module according to the first embodiment.
[0015] FIG. 3 is a schematic configuration diagram of an optical
module according to a second embodiment.
[0016] FIG. 4 describes the configuration of an optical module
according to Comparative Example.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
First Embodiment
[0017] A first embodiment of the present disclosure will be
described below with reference to FIGS. 1 and 2.
[0018] A projector according to the present embodiment is a
three-plate liquid crystal projector that uses three liquid crystal
panels as light modulators to display a color image on a screen
(projection receiving surface).
[0019] In the following drawings, components are drawn at different
dimensional scales in some cases for clarity of each of the
components.
[0020] FIG. 1 is a schematic configuration diagram showing the
optical system of a projector 1 according to the present
embodiment.
[0021] The projector 1 includes a first light source section 101, a
second light source section 102, a uniform illumination system 110,
a color separation/light guide system 200, an optical module 31,
and a projection optical apparatus 600, as shown in FIG. 1.
[0022] The optical module 31 includes a light modulation apparatus
400B for blue light (first light modulation apparatus), a light
modulation apparatus 400G for green light (second light modulation
apparatus), a light modulation apparatus 400R for red light (third
light modulation apparatus), and a light combiner 500.
[0023] The first light source section 101 includes a first light
source 20, a light focusing system 26, a diffuser plate 27, and a
collimation system 28.
[0024] The first light source 20 includes a plurality of
semiconductor laser devices 20a, which are each a solid-state light
source. The semiconductor laser devices 20a each output blue light
BL having emitted light intensity that peaks, for example, at a
wavelength of 460 nm. The first light source 20 may instead be
formed of a single semiconductor laser device 20a. The first light
source 20 may still instead be formed of semiconductor laser
devices each outputting blue light having a peak wavelength other
than 460 nm. The semiconductor laser devices 20a may each instead
output blue light BL having emitted light intensity that peaks, for
example, at a wavelength ranging from 430 nm to 480 nm.
[0025] The light focusing system 26 includes a first lens 26a and a
second lens 26b. The light focusing system 26 focuses the blue
light outputted from the first light source 20 on the downstream
diffuser plate 27 or in the vicinity thereof. The first lens 26a
and the second lens 26b are each formed of a convex lens.
[0026] The diffuser plate 27 diffuses the blue light BL outputted
from the first light source 20 to convert the blue light BL into
blue light BL having a light orientation distribution close to the
light orientation distribution of fluorescence Y outputted from a
downstream wavelength converter 30. The diffuser plate 27 can be
formed, for example, of a ground glass plate made of optical
glass.
[0027] The collimation system 28 includes a first lens 28a and a
second lens 28b. The collimation system 28 substantially
parallelizes the light having exited out of the diffuser plate 27.
The first lens 28a and the second lens 28b are each formed of a
convex lens.
[0028] The second light source section 102 includes a second light
source 10, a collimation system 70, a dichroic mirror 80, a
collimation/light focusing system 90, and a wavelength converter
30.
[0029] The second light source 10 includes a plurality of
semiconductor laser devices 10a. The semiconductor laser devices
10a each output blue light E having emitted light intensity that
peaks, for example, at a wavelength of 445 nm. The second light
source 10 may instead be formed of a single semiconductor laser
device 10a. The second light source 10 may still instead be formed
of semiconductor laser devices each outputting blue light having a
peak wavelength other than 445 nm. The semiconductor laser devices
10a may each instead output blue light E having emitted light
intensity that peaks, for example, at a wavelength ranging from 430
nm to 480 nm.
[0030] The collimation system 70 includes a first lens 72 and a
second lens 74. The collimation system. 70 substantially
parallelizes the blue light E outputted from the second light
source 10. The first lens 72 and the second lens 74 are each formed
of a convex lens.
[0031] The dichroic mirror 80 is so disposed in the optical path of
the blue light E between the collimation system 70 and the
collimation/light focusing system 90, which will be described
later, as to intersect an optical axis ax of the second light
source 10 and an illumination optical axis 100ax at 45.degree.. The
dichroic mirror 80 reflects the blue lights BL and E and transmits
the fluorescence Y, which is yellow fluorescence containing red
light and green light.
[0032] The collimation/light focusing system 90 includes a first
lens 92 and a second lens 94. The collimation/light focusing system
90 substantially focuses the blue light E reflected off the
dichroic mirror 80, causes the substantially focused blue light E
to enter a phosphor layer 42 of the wavelength converter 30, which
will be described later, and substantially parallelizes the
fluorescence Y outputted from the wavelength converter 30. The
first lens 92 and the second lens 94 are each formed of a convex
lens.
[0033] The wavelength converter 30 includes a disc 40, a reflection
film 41, the phosphor layer 42, and a motor 50. The disc 40 can be
rotated by the motor 50. The phosphor layer 42 is annually provided
on an upper surface 40a of the disc 40 along the circumferential
direction thereof. The motor 50 is disposed on the side facing a
lower surface 40b of the disc 40, and a rotary shaft 50a of the
motor 50 is connected to the disc 40.
[0034] The phosphor layer 42 converts the blue light E outputted
from the second light source 10 into the fluorescence Y, which
belongs to a wavelength band ranging, for example, from 520 nm to
580 nm. The fluorescence Y is yellow light containing red light and
green light. An antireflection film (not shown) for preventing
reflection of the blue light E is provided on the surface of the
phosphor layer 42.
[0035] Since the blue light E formed of laser beams enters the
phosphor layer 42, heat is generated in the phosphor layer and
degrades the function thereof. In the present embodiment, the disc
40 is rotated to successively change the light incident position on
the phosphor layer 42 where the blue light E is incident. The thus
configured wavelength converter 30 prevents the same location of
the phosphor layer 42 from being irradiated with the blue light E
in a concentrated manner and therefore prevents degradation of the
phosphor layer 42.
[0036] In the present embodiment, the phosphor layer 42 is formed,
for example, of a ceramic phosphor layer, which suppresses an
increase in temperature of the phosphor layer 42 and therefore
suppresses light emission failure called temperature quenching. The
phosphor layer 42 is formed, for example, of a bulk (block-shaped)
YAG-based phosphor made, for example, of (Y, Gd)3(Al, Ga)5012:Ce.
The thus formed phosphor layer 42 can emit the fluorescence Y at
high efficiency.
[0037] The blue light BL outputted from the first light source 20
is reflected off the dichroic mirror 80 and then combined with the
yellow fluorescence Y having been outputted from the wavelength
converter 30 and having passed through the dichroic mirror 80 to
form white light W. The white light W enters the uniform
illumination system 110.
[0038] The uniform illumination system 110 includes a first lens
array 120, a second lens array 130, a polarization converter 140,
and a superimposing lens 150.
[0039] The first lens array 120 includes a plurality of first
lenses 122, which divide the light having passed through the
dichroic mirror 80 into a plurality of sub-light fluxes. The
plurality of first lenses 122 are arranged in a matrix in a plane
perpendicular to the illumination optical axis 100ax.
[0040] The second lens array 130 includes a plurality of second
lenses 132 corresponding to the plurality of first lenses 122 of
the first lens array 120. The second lens array 130 along with the
superimposing lens 150 forms images of the first lenses 122 of the
first lens array 120 in the vicinity of an image formation area of
each of the light modulation apparatuses 400R, 400G, and 400B. The
plurality of second lenses 132 are arranged in a matrix in a plane
perpendicular to the illumination optical axis 100ax.
[0041] The polarization converter 140 converts each of sub-light
fluxes divided by the first lens array 120 into linearly polarized
light. The polarization converter 140 includes, although not shown,
polarization separation layers, reflection layers, and retardation
layers. The polarization separation layers directly transmit one
linearly polarized component out of the polarization components
contained in the light from the wavelength converter 30 and reflect
another linearly polarized component toward the reflection layers.
The reflection layers reflect the other linearly polarized
component reflected off the polarization separation layers in the
direction parallel to the illumination optical axis 100ax. The
retardation layers convert the other linearly polarized component
reflected off the reflection layers into the one linearly polarized
component.
[0042] The superimposing lens 150 collects the sub-light fluxes
from the polarization converter 140 and superimposes the collected
sub-light fluxes on one another in the vicinity of the image
formation area of each of the light modulation apparatuses 400R,
400G, and 400B. The first lens array 120, the second lens array
130, and the superimposing lens 150 form an optical integration
system that homogenizes the in-plane optical intensity distribution
of the light having exited out of the wavelength converter 30.
[0043] The color separation/light guide system 200 includes a
dichroic mirror 210, a dichroic mirror 220, a reflection mirror
230, a reflection mirror 240, a reflection mirror 250, a relay lens
260, and a relay lens 270. The color separation/light guide system
200 separates the white light W into red light LR, green light LG,
and blue light LB, guides the red light LR to the light modulation
apparatus 400R for red light, guides the green light LG to the
light modulation apparatus 400G for green light, and guides the
blue light LB to the light modulation apparatus 400B for blue
light.
[0044] A field lens 300R is disposed between the color
separation/light guide system 200 and the light modulation
apparatus 400R for red light. A field lens 300G is disposed between
the color separation/light guide system 200 and the light
modulation apparatus 400G for green light. A field lens 300B is
disposed between the color separation/light guide system 200 and
the light modulation apparatus 400B for blue light.
[0045] In the present embodiment, the red light LR corresponds to
light that belongs to a wavelength band ranging from 590 nm to 700
nm. The green light LG corresponds to light that belongs to a
wavelength band ranging from 480 nm to 590 nm. The blue light LB
corresponds to light that belongs to a wavelength band ranging from
430 nm to 480 nm.
[0046] The dichroic mirror 210 transmits the red light component
and reflects the green light component and the blue light
component. The dichroic mirror 220 reflects the green light
component and transmits the blue light component. The reflection
mirror 230 reflects the red light component. The reflection mirrors
240 and 250 reflect the blue light component.
[0047] The red light LR having passed through the dichroic mirror
210 is reflected off the reflection mirror 230, passes through the
field lens 300R, and is incident on the image formation area of the
light modulation apparatus 400R for red light. The green light LG
reflected off the dichroic mirror 210 is further reflected off the
dichroic mirror 220, passes through the field lens 300G, and is
incident on the image formation area of the light modulation
apparatus 400G for green light. The blue light LB having passed
through the dichroic mirror 220 travels via the relay lens 260, the
reflection mirror 240, the relay lens 270, the reflection mirror
250, and the field lens 300B and is incident on the image formation
area of the light modulation apparatus 400B for blue light.
[0048] The light modulation apparatuses 400R, 400G, and 400B each
include a liquid crystal panel. The light modulation apparatuses
400R, 400G, and 400B each modulate the color light incident thereon
in accordance with image information to form an image corresponding
to the color light. The configuration of the light modulation
apparatuses 400R, 400G, and 400B will be described later in
detail.
[0049] The light combiner 500 is formed of a cross dichroic prism.
The light combiner 500 combines the image light outputted from the
light modulation apparatus 400R, the image light outputted from the
light modulation apparatus 400G, and the image light outputted from
the light modulation apparatus 400B with one another. The
cross-dichroic prism is formed of four right-angled prisms bonded
to each other and therefore has a substantially square shape in the
plan view, and dielectric multilayer films are formed on the
substantially X-letter-shaped interfaces between the right-angled
prisms bonded to each other.
[0050] The image light having exited out of the light combiner 500
is enlarged and projected by the projection optical apparatus 600
and form an image on a screen SCR. That is, the projection optical
apparatus 600 projects light modulated by each of the light
modulation apparatuses 400R, 400G, and 400B on the screen SCR. The
projection optical apparatus 600 is formed of a plurality of
lenses.
[0051] The optical module 31 will be described below.
[0052] FIG. 2 is a schematic configuration diagram of the optical
module 31 according to the present embodiment.
[0053] The optical module 31 includes the light modulation
apparatus 400B for blue light, the light modulation apparatus 400G
for green light, the light modulation apparatus 400R for red light,
and the light combiner 500, as shown in FIG. 2.
[0054] The light modulation apparatus 400B for blue light includes
a light-incident-side polarizing plate 401B, a light modulator 402B
for blue light, a first light-exiting-side polarizing plate 403B
(first polarizer), and a second light-exiting-side polarizing plate
404B (second polarizer).
[0055] Similarly, the light modulation apparatus 400G for green
light includes a light-incident-side polarizing plate 401G, a light
modulator 402G for green light, a first light-exiting-side
polarizing plate 403G (first polarizer), and a second
light-exiting-side polarizing plate 404G (second polarizer).
[0056] The light modulation apparatus 400R for red light includes a
light-incident-side polarizing plate 401R, a light modulator 402R
for red light, a first light-exiting-side polarizing plate 403R
(first polarizer), and a second light-exiting-side polarizing plate
404R (second polarizer).
[0057] In the present embodiment, the polarizing plates in the
light modulator 400B for blue light, the light modulator 400G for
green light, and the light modulator 400R for red light have a
common configuration and arrangement. The light modulation
apparatus 400B for blue light will therefore be described below as
a representative light modulation apparatus, and the other light
modulation apparatuses will not be described.
[0058] In the light modulation apparatus 400B for blue light, the
light modulator 402B for blue light is formed of a transmissive
liquid crystal panel including two light transmissive substrates
and a liquid crystal layer. The light modulator 402B for blue light
may include dustproof glass plates on the light incident side and
the light exiting side of the liquid crystal panel described above.
A method for driving the liquid crystal panel is not limited to a
specific method, such as a longitudinal electric field method or a
transverse electric field method.
[0059] The first light-exiting-side polarizing plate 403B is
disposed on the downstream of the light modulator 402B for blue
light, that is, on the light exiting side of the light modulator
402B for blue light. The first light-exiting-side polarizing plate
403B includes a first base 61, a first inorganic polarization layer
62, and a first light absorbing layer 63.
[0060] The first base 61 is formed of a light transmissive
substrate and has a first surface 61a and a second surface 61b. The
light transmissive substrate is made, for example, of low thermal
expansion glass, such as quartz and crystallized glass. The light
transmissive substrate may be made, for example, of alkali-free
glass in place of low thermal expansion glass.
[0061] The first inorganic polarization layer 62 is formed of a
wire-grid polarization layer provided on the first surface 61a of
the first base 61. The wire-grid polarization layer is one type of
structural birefringent polarization layer and has a structure in
which minute ribs (not shown) extending in one direction are formed
on a metal thin film formed on the first base 61. The metal thin
film can be made of a metal, such as aluminum and tungsten, and
formed by evaporation or sputtering. The ribs can be formed by the
combination of a light exposure technology, such as a two-beam
interference light exposure, electron drawing, and X-ray
lithography, and an etching technology.
[0062] The ribs are formed at intervals shorter than the wavelength
of the blue light LB incident on the light modulator 402B for blue
light. The first inorganic polarization layer 62 can therefore
reflect linearly polarized light having a polarization direction
parallel to the direction in which the ribs extend and transmit
linearly polarized light having a polarization direction
perpendicular to the direction in which the ribs extend. The
wire-grid polarization layer is made of an inorganic material and
therefore extremely excels in heat resistance and hardly absorbs
light.
[0063] The first light absorbing layer 63 is so provided as to face
the first base 61 with the first inorganic polarization layer 62
sandwiched therebetween. That is, the first light absorbing layer
63 is layered on the first inorganic polarization layer 62 over the
first surface 61a of the first base 61. The first light absorbing
layer 63 is made of a material that absorbs light. The first light
absorbing layer 63 absorbs part of the light incident thereon. The
first light absorbing layer 63 therefore absorbs part of the light
externally and directly incident on the first light absorbing layer
63 or part of the light reflected off the first inorganic
polarization layer 62.
[0064] The second light-exiting-side polarizing plate 404B is
disposed on the downstream of the first light-exiting-side
polarizing plate 403B, that is, on the light exiting side of the
first light-exiting-side polarizing plate 403B. The second
light-exiting-side polarizing plate 404B includes a second base 65,
a second inorganic polarization layer 66, and a second light
absorbing layer 67.
[0065] The second base 65 is formed of a light transmissive
substrate made, for example, of glass and has a third surface 65a
and a fourth surface 65b. The light transmissive substrate is made,
for example, of free-alkali glass. The light transmissive substrate
may be made of low thermal expansion glass, such as quartz and
crystallized glass, as is the first base 61 in place of alkali-free
glass.
[0066] The second inorganic polarization layer 66 is formed of a
wire-grid polarization layer provided on the third surface 65a of
the second base 65. The configuration of the wire-grid polarization
layer is the same as that of the wire-grid polarization layer that
forms the first inorganic polarization layer 62.
[0067] The second light absorbing layer 67 is so provided as to
face the second base 65 with the second inorganic polarization
layer 66 sandwiched therebetween. That is, the second light
absorbing layer 67 is layered on the second inorganic polarization
layer 66 over the third surface 65a of the second base 65. The
configuration of the second light absorbing layer 67 is the same as
that of the first light absorbing layer 63.
[0068] The first light-exiting-side polarizing plate 403B is so
disposed that the first light absorbing layer 63 faces a light
exiting surface 402c of the light modulator 402B for blue light.
The second light-exiting-side polarizing plate 404B is so disposed
that the fourth surface 65b of the second base 65 faces the second
surface 61b of the first base 61. In other words, the second
light-exiting-side polarizing plate 404B is so disposed that the
second light absorbing layer 67 faces the light combiner 500. The
first light-exiting-side polarizing plate 403B and the second
light-exiting-side polarizing plate 404B are thus so disposed that
the first base 61 and the second base 65 face each other.
[0069] The light-incident-side polarizing plate 401B is disposed on
the upstream of the light modulator 402B for blue light, that is,
on the light incident side of the light modulator 402B for blue
light. The light-incident-side polarizing plate 401B includes a
third base 75, a third inorganic polarization layer 76, and a third
light absorbing layer 77. The configuration of the
light-incident-side polarizing plate 401B is the same as those of
the first light-exiting-side polarizing plate 403B and the second
light-exiting-side polarizing plate 404B. The light-incident-side
polarizing plate 401B is so disposed that the third light absorbing
layer 77 faces a light incident surface 402d of the light modulator
402B for blue light.
[0070] An optical module according to Comparative Example including
a single light-exiting-side polarizing plate will now be
described.
[0071] FIG. 4 describes the configuration of an optical module 750
according to Comparative Example.
[0072] In FIG. 4, no light modulation apparatus for blue light or
light modulation apparatus for red light is shown.
[0073] The optical module 750 according to Comparative Example
includes a light modulation apparatus 700G for green light and a
light combiner 770, as shown in FIG. 4. The light modulation
apparatus 700G for green light include a light-incident-side
polarizing plate 701G, a light modulator 702G for green light, and
alight-exiting-side polarizing plate 703G.
[0074] The light-incident-side polarizing plate 701G includes a
base 86, an inorganic polarization layer 87 formed of a wire-grid
polarization layer, and a light absorbing layer 88. The
light-exiting-side polarizing plate 703G includes a base 96, an
inorganic polarization layer 97 formed of a wire-grid polarization
layer, and a light absorbing layer 98. The light-exiting-side
polarizing plate 703G is so disposed that the light absorbing layer
98 faces a light exiting surface 702c of the light modulator 702G
for green light.
[0075] In the optical module 750 according to Comparative Example,
assume that the light having exited out of the light-exiting-side
polarizing plate 703G is reflected off a projection lens 780 or the
light combiner 770. In this case, the light has a specific
polarization direction at the point when the light exits out of the
light-exiting-side polarizing plate 703G, but the polarization
direction of the light is disturbed when the light is reflected off
the projection lens 780 or the light combiner 770 or passes through
the bases of the light-exiting-side polarizing plate 703G and the
light combiner 770. Reflected light LF1 and reflected light LF2 are
each therefore a mixture of light fluxes having different
polarization directions.
[0076] When the reflected light LF1 and the reflected light LF2
reach a boundary surface K between the inorganic polarization layer
97 and the base 96 of the light-exiting-side polarizing plate 703G,
the reflected light LF1 and the reflected light LF2 are reflected
off the boundary surface K because the inorganic polarization layer
97 is made of aluminum, which has high reflectance, and the
boundary surface K has no light absorbing layer. The reflected
light LF1 and the reflected light LF2 reflected off the boundary
surface K therefore form stray light and return light in the space
between the light-exiting-side polarizing plate 703G and the
projection lens 780 or the light combiner 770, resulting in a ghost
and light leakage on the screen due to the stray light and return
light in some cases.
[0077] In contrast, in the optical module 31 according to the
present embodiment, the second light absorbing layers 67 of the
second light-incident-side polarizing plates 404B, 404G, and 404R
face the light combiner 500. Therefore, even when reflected light
from the projection optical apparatus 600 or the light combiner 500
returns to the second light-incident-side polarizing plates 404B,
404G, and 404R, at least part of the reflected light is absorbed by
the second light absorbing layers 67. The stray light and return
light that occur in the spaces between the second
light-incident-side polarizing plates 404B, 404G, 404R and the
projection optical apparatus 600 or the light combiner 500 can be
suppressed, thus a ghost and light leakage on the screen SCR can be
reduced.
[0078] Further, in the optical module 31 according to the present
embodiment, since the first light absorbing layers 63 of the first
light-incident-side polarizing plates 403B, 403G, and 403R face the
light modulators 402B, 402G, and 402R, stray light and return light
formed of light reflected off the first inorganic polarization
layers 62 and returning to the light modulators 402B, 402G, and
402R can be suppressed. Moreover, the first base 61 is not present
between each of the light modulators 402B, 402G, and 402R and the
first inorganic polarization layer 62, so that the light having
exited out of each of the light modulators 402B, 402G, and 402R is
incident on the first inorganic polarization layer 62 before
passing through the first base 61. The disturbance of the
polarization direction that occurs when the light passes through
the first bases 61 can therefore be suppressed, whereby a decrease
in contrast of a projection image can be suppressed.
[0079] Further, in the optical module 31 according to the present
embodiment, in which the third light absorbing layers 77 of the
light-incident-side polarizing plates 401B, 401G, and 401R face the
light modulators 402B, 402G, and 402R, the third base 75 is not
present in the space between the third inorganic polarization
layers 76 and each of the light modulators 402B, 402G, and 402R, so
that the light having exited out of the third inorganic
polarization layers 76 does not pass through the third bases 75 but
is incident on the light modulators 402B, 402G, and 402R. The
disturbance of the polarization direction that occurs when the
light passes through the third bases 75 can therefore be
suppressed, whereby a decrease in contrast of a projection image
can be suppressed.
[0080] In the optical module 31 according to the present
embodiment, the first bases 61 of the first light-incident-side
polarizing plates 403B, 403G, and 403R and the second bases 65 of
the second light-exiting-side polarizing plates 404B, 404G, and
404R are each made of low thermal expansion glass. Therefore, even
when heat is generated when the light enters the first
light-incident-side polarizing plates 403B, 403G, and 403R and the
second light-exiting-side polarizing plates 404B, 404G, and 404R,
distortion of the first bases 61 and the second bases 65 due to the
heat can be suppressed to a small value. Therefore, even when the
temperatures of the first bases 61 and the second bases 65
increase, disturbance of the polarization direction of the light
passing through the first bases 61 and the second bases 65 can be
suppressed, whereby a decrease in contrast of a projection image
can be suppressed.
[0081] In the optical module 31 according to the present
embodiment, in which two polarizing plates are provided on the
downstream of each of the light modulators 402B, 402G, and 402R,
that is, on the first light-incident-side polarizing plates 403B,
403G, and 403R and the second light-exiting-side polarizing plates
404B, 404G, and 404R, the extinction ratio of the entire
light-exiting-side polarizing plates can be increased as compared
with that when one polarizing plate is provided. As a result, the
present embodiment allows an increase in contrast of a projection
image.
[0082] The projector 1 according to the present embodiment, which
includes the optical module 31 described above, excels in quality
of a projection image.
Second Embodiment
[0083] A second embodiment of the present disclosure will be
described below with reference to FIG. 3.
[0084] The configuration of a projector according to the second
embodiment is the same as that in the first embodiment, and the
configuration of the optical module differs from that in the first
embodiment. The entire projector will therefore not be
described.
[0085] FIG. 3 is a schematic configuration diagram of an optical
module 32 according to the second embodiment.
[0086] In FIG. 3, components common to those in FIG. 2 in the first
embodiment have the same reference characters and will not be
described.
[0087] The optical module 32 according to the present embodiment
includes a light modulation apparatus 800B for blue light, a light
modulation apparatus 800G for green light, a light modulation
apparatus 800R for red light, and the light combiner 500, as shown
in FIG. 3.
[0088] The light modulation apparatus 800B for blue light includes
a retardation film 805B, the light-incident-side polarizing plate
401B, the light modulator 402B for blue light, an optical
compensation plate 806B, the first light-exiting-side polarizing
plate 403B (first polarizer), a heat dissipating plate 807B, the
second light-exiting-side polarizing plate 404B (second
polarizer).
[0089] The light modulation apparatus 800G for green light includes
the light-incident-side polarizing plate 401G, the light modulator
402G for green light, an optical compensation plate 806G, a
light-exiting-side polarizing plate 808G, and a heat dissipating
plate 807G.
[0090] The light modulation apparatus 800R for red light includes
the light-incident-side polarizing plate 401R, the light modulator
402R for red light, an optical compensation plate 806R, the first
light-exiting-side polarizing plate 403R, a heat dissipating plate
807R, and a second light-exiting-side polarizing plate 809R, and a
retardation film 805R.
[0091] As described above, in the second embodiment, the light
modulation apparatus 800B for blue light, the light modulation
apparatus 800G for green light, and the light modulation apparatus
800R for red light have configurations differed from one another,
unlike in the first embodiment. Specifically, in the second
embodiment, the light modulation apparatus 800B for blue light
includes two inorganic polarization plates on the downstream of the
light modulator 402B for blue light, the light modulation apparatus
800G for green light includes one inorganic polarization plate on
the downstream of the light modulator 402G for green light, and the
light modulation apparatus 800R for red light includes one
inorganic polarization plate and one organic polarization plate on
the downstream of the light modulator 402R for red light.
[0092] In the light modulation apparatus 800B for blue light, the
retardation film 805B is disposed on the upstream of the
light-incident-side polarization plate 401B, that is, on the light
incident side of the light-incident-side polarization plate 401B.
The retardation film 805B is formed of a half-wave plate. The
retardation film 805B imparts retardation corresponding to half the
wavelength of the light passing through the retardation film 805B
to the light. First linearly polarized light (P-polarized light,
for example) incident on the retardation film 805B is therefore
converted into second linearly polarized light (S-polarized light,
for example) having a polarization direction perpendicular to the
polarization direction of the first linearly polarized light when
passing through the retardation film 805B.
[0093] The light-incident-side polarization plate 401B is disposed
on the upstream of the light modulator 402B for blue light, that
is, on the light incident side of the light modulator 402B for blue
light. The light-incident-side polarization plate 401B includes the
third base 75, the third inorganic polarization layer 76, and the
third light absorbing layer 77. The light-incident-side
polarization plate 401B is so disposed that the third light
absorbing layer 77 faces the light incident surface 402d of the
light modulator 402B for blue light.
[0094] The light modulator 402B for blue light is formed of a
transmissive liquid crystal panel containing two light transmissive
substrates and a liquid crystal layer. The light modulator 402B for
blue light may include dustproof glass plates on the light incident
side and the light exiting side of the liquid crystal panel
described above. A method for driving the liquid crystal panel is
not limited to a specific method, such as a longitudinal electric
field method or a transverse electric field method.
[0095] The optical compensation plate 806B is disposed on the
downstream of the light modulator 402B for blue light, that is, on
the light exiting side of the light modulator 402B for blue light.
In the case of a liquid crystal projector, when light leakage
occurs when light obliquely passes through the light modulator, the
contrast of an image decreases. The optical compensation plate
806B, which compensates the retardation of the light obliquely
passing through the light modulator, can suppress a decrease in the
contrast.
[0096] The first light-exiting-side polarization plate 403B is
disposed on the downstream of the optical compensation plate 806B,
that is, on the light exiting side of the optical compensation
plate 806B. The first light-exiting-side polarization plate 403B
includes the first base 61, the first inorganic polarization layer
62 formed of a wire-grid polarization layer, and the first light
absorbing layer 63. The configuration of the first
light-exiting-side polarization plate 403B is the same as that of
the first light-exiting-side polarization plate in the first
embodiment.
[0097] The heat dissipating plate 807B is disposed on the
downstream of the first light-exiting-side polarization plate 403B,
that is, on the light exiting side of the first light-exiting-side
polarization plate 403B. The heat dissipating plate 807B is formed
of a plate made, for example, of sapphire glass having high thermal
conductivity and high optical transparency. The heat dissipating
plate 807B may be in contact with the first light-exiting-side
polarization plate 403B or may be slightly separate from the first
light-exiting-side polarization plate 403B. Out of the two
light-exiting-side polarization plates 403B and 404B, heat is
likely to be generated in the first light-exiting-side polarization
plate 403B, on which light is first incident. In view of the fact
described above, the heat dissipating plate 807B, which dissipates
the heat in the first light-exiting-side polarization plate 403B
out thereof, can suppress an increase in temperature of the first
light-exiting-side polarization plate 403B and can therefore ensure
the reliability of the first light-exiting-side polarization plate
403B.
[0098] The second light-exiting-side polarization plate 404B is
disposed on the downstream of the heat dissipating plate 807B, that
is, on the light exiting side of the heat dissipating plate 807B.
The second light-exiting-side polarization plate 404B includes the
second base 65, the second inorganic polarization layer 66, and the
second light absorbing layer 67. The configuration of the second
light-exiting-side polarization plate 404B is the same as that of
the second light-exiting-side polarization plate in the first
embodiment.
[0099] The first light-exiting-side polarization plate 403B is so
disposed that the first light absorbing layer 63 faces the light
exiting surface 402c of the light modulator 402B for blue light
with the optical compensation plate 806B sandwiched therebetween.
The second light-exiting-side polarization plate 404B is so
disposed that the fourth surface 65b of the second base 65 faces
the second surface 61b of the first base 61 with the heat
dissipating plate 807B sandwiched therebetween. In other words, the
second light-exiting-side polarization plate 404B is so disposed
that the second light absorbing layer 67 faces the light combiner
500.
[0100] In the light modulation apparatus 800G for green light, the
light-exiting-side polarization plate 808G is disposed on the
downstream of the light modulator 402G for green light, that is, on
the light exiting side of the light modulator 402G for green light.
The light-exiting-side polarization plate 808G includes the base
61, the inorganic polarization layer 62, a first light absorbing
layer 68, and a second light absorbing layer 69. In the case of the
light modulation apparatus 800G for green light, in which only one
light-exiting-side polarization plate 808G is provided, the second
light absorbing layer 69 is provided between the base 61 and the
inorganic polarization layer 62 in order to suppress stray light
and return light formed of light reflected off the inorganic
polarization layer 62 and returning to the light combiner 500 in
addition to the first light absorbing layer 68.
[0101] In the light modulation apparatus 800R for red light, the
first light-exiting-side polarization plate 403R is disposed on the
downstream of the light modulator 402R for red light, that is, on
the light exiting side of the light modulator 402R for red light.
The first light-exiting-side polarization plate 403R includes the
first base 61, the first inorganic polarization layer 62 formed of
a wire-grid polarization layer, and the first light absorbing layer
63. The configuration of the first light-exiting-side polarization
plate 403R is the same as that of the first light-exiting-side
polarization plate in the first embodiment.
[0102] The heat dissipating plate 807R is disposed on the
downstream of the first light-exiting-side polarization plate 403R,
that is, on the light exiting side of the first light-exiting-side
polarization plate 403R. The configuration of the heat dissipating
plate 807R is the same as that of the heat dissipating plate 807B
in the light modulation apparatus 800B for blue light.
[0103] The second light-exiting-side polarization plate 809R is
disposed on the downstream of the heat dissipating plate 807R, that
is, on the light exiting side of the heat dissipating plate 807R.
The second light-exiting-side polarization plate 809R is formed of
an organic polarization plate made of a resin material. The degree
of polarization provided by the second light-exiting-side
polarization plate 809R may be lower than the degree of
polarization provided by the first light-exiting-side polarization
plate 403R. For example, the ratio of the degree of polarization
between the first light-exiting-side polarization plate 403R and
the second light-exiting-side polarization plate 809R may be about
2:1.
[0104] The other configurations of the optical module 32 are the
same as those of the optical module 31 according to the first
embodiment.
[0105] Also in the optical module 32 according to the present
embodiment, the second light absorbing layer 67 of the second
light-exiting-side polarization plate 404B faces the light combiner
500 in the light modulation apparatus 800B for blue light.
Therefore, even when blue reflected light from the projection
optical apparatus 600 or the light combiner 500 returns to the
second light-incident-side polarizing plate 404B, at least part of
the blue reflected light is absorbed by the second light absorbing
layers 67. The stray light and return light of the blue light LB
that occur in the space between the second light-incident-side
polarizing plate 404B and the projection optical apparatus 600 or
the light combiner 500 can thus be suppressed.
[0106] As for the green light LG, the second light absorbing layer
69 of the light-exiting-side polarization plate 808G is so provided
as to face the light combiner 500, whereby the stray light and
return light that occur in the space between the inorganic
polarization layer 62 and the projection optical apparatus 600 or
the light combiner 500 can be suppressed.
[0107] As for the red light LR, the second light-exiting-side
polarization plate 809R formed of an organic polarization plate is
provided between the first light-exiting-side polarization plate
403R and the light combiner 500, whereby the reflected light from
the projection optical apparatus 600 or the light combiner 500 is
absorbed by the second light-exiting-side polarization plate 809R.
The optical module 32 according to the present embodiment can
therefore reduce the amount of reflected light from the projection
optical apparatus 600 or the light combiner 500 not only in the
light modulation apparatus 800B for blue light, which is the same
light modulation apparatus in the first embodiment, but in the
light modulation apparatus 800G for green light and the light
modulation apparatus 800R for red light, whereby a ghost and light
leakage on the screen SCR can be reduced.
[0108] In the optical module 32 according to the present
embodiment, the light modulation apparatus 800G for green light
uses only one light-exiting-side polarization plate 808G because
the contrast of the green light LG is originally high as compared
with the contrast of the blue light LB and the red light LR and it
is therefore unnecessary to particularly increase the extinction
ratio of the light-exiting-side polarization plate. Further, in the
light modulation apparatus 800R for red light, one of the two
light-exiting-side polarization plates is an organic polarization
plate because the energy of the red light RL is lower than the
energy of the blue light LB and the green light LG, and no problem
therefore occurs with the reliability of the polarization plate.
The different configurations of the light modulation apparatuses on
the color light basis described above therefore allow
simplification and cost reduction of the configuration of the
optical module 32.
[0109] Also in the optical module 32 according to the present
embodiment, the same effect provided in the first embodiment can be
provided. For example, the first light absorbing layers 63 of the
first light-exiting-side polarization plates 403B and 403R and the
first light absorbing layer 68 of the light-exiting-side
polarization plate 808G face the light modulating devices 402B,
402R, and 402G, and the third light absorbing layers 77 of the
light-incident-side polarization plates 401B, 401G, and 401R face
the light modulating devices 402B, 402G, and 402R, whereby a
decrease in contrast of a projection image can be suppressed.
[0110] The technical range of the present disclosure is not limited
to the embodiments described above, and a variety of changes can be
made thereto to the extent that the changes do not depart from the
substance of the present disclosure.
[0111] For example, the above embodiments have been presented with
reference to the case where the first and second inorganic
polarization layers are each formed of a wire-grid polarization
layer. The first and second inorganic polarization layers may
instead be each formed of an inorganic polarization layer so formed
that inorganic materials are layered on each other in place of a
wire-grid polarization layer.
[0112] The first embodiment has been presented with reference to
the case where the configuration of the light modulation apparatus
according to the present disclosure is applied to all the light
modulation apparatus for blue light, the light modulation apparatus
for green light, and the light modulation apparatus for red light,
and the second embodiment has been presented with reference to the
case where the configuration of the light modulation apparatus
according to the present disclosure is applied to only the light
modulation apparatus for blue light. However, the present
disclosure is not limited to these configurations. The
configuration of the light modulation apparatus according to the
present disclosure may be applied to at least one the light
modulation apparatus for blue light, the light modulation apparatus
for green light, and the light modulation apparatus for red
light.
[0113] In addition to the above, the shape, the number, the
arrangement, the material, and other specific descriptions of the
light modulation apparatus, the optical module, and the projector
are not limited to those in the embodiments described above and can
be changed as appropriate. In the projector according to the
embodiments described above, a light source apparatus including a
wavelength converter containing a phosphor and an excitation light
source has been presented by way of example, but not necessarily.
For example, a light source apparatus including a discharge lamp
may be used, or a light source apparatus including a solid-state
light source, such as a laser light source and a light emitting
diode light source, may be used.
* * * * *